Simon S Lo, M.D.Director of Radiosurgery Services and Neurologic Radiation OncologyUniversity Hospital Seidman Cancer CenterAssociate Professor of Radiation OncologyCase Western Reserve University Cleveland, OHUSA
Clinical Aspects of LINAC-based Stereotactic Body Radiation Therapy
University Hospitals Seidman Cancer Center, Case Western Reserve University
Conflicts of interest: None
Financial Disclosure: None
Disclosure:
Chair, American College of Radiology Appropriateness Criteria Expert Panel in Bone Metastasis
Stereotactic Body Radiation Therapy(Also known as Stereotactic Ablative Radiotherapy)
• SBRT utilizes ultra-high ablative doses of radiation, typically 10-20 Gy per fraction, delivered to the planning treatment volume in 1-5 fractions
• A “spin-off” of Gamma Knife radiosurgery• First started in Sweden (Lax and Blomgren)
and Japan (Uematsu) based on LINAC
What is LINAC-based SBRT?
• In actual fact, all devices, except proton beam machines, used to delivered photon-based SBRT are LINACs
• Practically, SBRT delivered using any LINAC except CyberKnife can be referred to as LINAC-based SBRT
University Hospitals Seidman Cancer Center, Case Western Reserve University
Courtesy of Dr. Eric Chang, USC
Clinical applications
• Stage I non-small cell lung cancer• Oligometastases in lung and liver• Primary liver tumors including HCC• Prostate cancer• Pancreatic cancer• Spinal metastases
Newer clinical applications
• Renal cell cancer• Benign spinal tumors• Adrenal metastases• Head and neck cancer• Spinal cord compression• Breast cancer• Gynecologic cancer
Characteristics of SBRT/ SABR
• Secure robust immobilization avoiding patient movement for the typical long treatment sessions
• Accurate repositioning from simulation to treatment• Rigorous accounting of organ motion• Minimization of normal tissue exposure attained by using
multiple (eg, 10 or more) or large-angle arcing small aperture fields
• Stereotactic registration (ie, via fiducial markers or surrogates) of tumor targets and normal tissue avoidance structures to the treatment delivery machine
• Ablative dose fractionation delivered to the patient with subcentimeter accuracy
Timmerman et al. JCO 2007
Robotic vs. LINAC-based SBRT
University Hospitals Seidman Cancer Center
Technical aspects
• Immobilization:
• Body frames• Vacuum pillows• Thermoplastic device • Frameless system
• Select the right device for the right disease site!
UH Seidman Cancer Center
Immobilization
UH Seidman Cancer Center
Immobilization
Immobilization
• University of Toronto study
• Evacuated cushion vs. Semirigid vacuum body fixation vs. Thermoplastic S-frame
• 84 patients with 102 spinal metastases• 4 sets of CBCT: Localization, verification,
mid-treatment, and post-treatment• No correction for rotation (≤2⁰)
Li et al. IJROBP 2012
Immobilization
Li et al. IJROBP 2012
Method of immobilization
Margins needed for verification CBCT
Margins needed for mid-treatment CBCT
Margins needed for post-treatment CBCT
Evacuated cushion (N = 24)
≤ 2 mm ≤ 2 mm > 2 mm (R-L and C-C)
Vacuum fixation (N = 60)
≤ 2 mm ≤ 2 mm ≤ 2 mm
Themoplastic S-frame (N = 18)
≤ 2 mm ≤ 2 mm > 2 mm (R-L and A-P)
Respiratory motion control
• Motion dampening- Abdominal compression, ABC
• Motion gating- Fiducials• Motion tracking- Fiducials and Synchrony
with CyberKnife
Timmerman JCO 2006; Lo NRCO 2010
UH Seidman Cancer Center
Abdominal Compression
Slide courtesy of Robert D. Timmerman, M.D.
UH Seidman Cancer Center
Motion management
Giuliani and Bezjak. In: Stereotactic Body Radiation Therapy: Lung Cancer (Eds: Lo, Teh, Mayr, Machtay). Future Medicine, UK.
UH Seidman Cancer Center
Factor in tumor motion
• Generic PTV expansion
• 4D CT (Internal Target Volume)
• 3 phase CT (free breathing, deep expiration and deep inspiration)
University Hospitals Seidman Cancer Center
Factor in tumor motion
GTV- Light blue
ITV- Purple
PTV- Red
University Hospitals Seidman Cancer Center
Factor in tumor motion
GTVGTV
PTVPTV
Abdominal compression- Verify under fluoroscopyIU/ Karolinska technique- GTV + 0.5 cm radially and 1.0 cm sup-inf = PTV
UH Seidman Cancer Center
Treatment planning
Slide courtesy of Robert D. Timmerman, M.D.
UH Seidman Cancer Center
Treatment planning
3DCRT techniqueIsotropic isodose distribution
UH Seidman Cancer Center
Treatment planning
Kuijper et al. RTO 2010
UH Seidman Cancer Center
Treatment planning
No significance difference in delivery time compared to IMRT if 2-3 arcs used for VMAT
Kuijper et al. RTO 2010
UH Seidman Cancer Center
Treatment planning
UH Seidman Cancer Center
Treatment planning
UH Seidman Cancer Center
Normal Tissue Constraints
Lo et al. Clinical Oncology 2012
UH Seidman Cancer Center
Normal Tissue Constraints
Lo et al. Clinical Oncology 2012
UH Seidman Cancer Center
Normal Tissue Constraints
Lo et al. Clinical Oncology 2012
UH Seidman Cancer Center
Image-guidance
MV CBCT
UH Seidman Cancer Center
Image-guidance
kV CBCT- Courtesy of Dr. Arjun Sahgal, U of Toronto
UH Seidman Cancer Center
Image-guidance
ExacTrac- Courtesy of Dr. Bin Teh
UH Seidman Cancer Center
Image-guidance
• CBCT vs. stereoscopic X-rays (ExacTrac)• Duke University study• Phantom study: Translational and rotational
discrepancies of < 1 mm and < 1o
Patient study: Translational and rotational discrepancies of < 2 mm and < 1.5o
Chang et al. Radiotherapy and Oncology 2010
UH Seidman Cancer Center
Image-guidance
Type of CBCT Resolution Metallic artifacts
kV CT Better Worse
MV CT Worse Better
Intrafractional monitoring
• Stereoscopic X-ray• Mid-way CT-on-rail• Mid-way kV or MV CBCT • Mid-way MVCT
Comparison of CyberKnife-based and LINAC-based SBRT
1. No real time tracking2. Very robust
immobilization is crucial especially for spinal SBRT
3. Mid-way OBI is needed to ensure positional accuracy
4. More manual work is needed for patient set-up
1. Better for posteriorlylocated lesions
2. Better from donut-shaped targets
3. More flexible beam angles4. Faster treatment delivery
especially for newer machines
5. Volumetric verification available
6. Better availability
LINAC-based
1. No posterior or posterior oblique beams
2. Long treatment delivery time
3. No volumetric verification4. Less availability
1. Near real time tracking2. Process is more
automated3. Very robust
immobilization not absolutely necessary
CyberKnife-based
Cons Pros Device
Stage I NSCLC
University Cancer Center
Hadziahmetovic et al. Discovery Medicine 2010
Lung oligometastasis
University Cancer Center
Lo et al. Nature Reviews Clinical Oncology 2011 (Authors retain ownership of copyright of contents)
Liver oligometastasis
University Cancer Center
Lo et al. Nature Reviews Clinical Oncology 2011 (Authors retain ownership of copyright of contents)
Hepatocellular carcinoma
University Cancer CenterLo et al. Discovery Medicine 2010
Prostate cancer
University Cancer CenterCourtesy of Dr. Andrew Loblaw, Odette Cancer Centre, University of Toronto
Pancreatic cancer
University Cancer Center
Chuong et al. IJROBP 2013
Spinal oligometastasis
University Cancer CenterLo et al. Discovery Medicine 2010
Spinal oligometastasis
University Cancer Center
Study/ Patient group
No. of patients/ sites
Apparatus used
Dose Follow-up Outcomes Toxicities
Wang (MDACC phase I/II trial)
149/ 166 LINAC 30 Gy in 5 fxs or 27 Gyin 3 fxs
15.9 months Absence of pain increased from 26% to 54% at 6 months1 and 2 year PFS: 80.5% and 72.4%
No grade 4 toxicities
Garg(MDACC phase I/II trial)
61/ 63 non-cervical lesions
LINAC 16-24 Gy in 1 fx
20 months 18-month actuarial imaging LC: 88%18-month OS: 64%
Two grade 3 or higher toxicities
Wang et a. Lancet Oncol 2012 and Garg et al. Cancer 2012
Renal Cell Carcinoma
University Cancer Center
From Teh et al. Renal Cell Carcinoma. In: Lo, Teh, Lu, Schefter. Stereotactic Body Radiation Therapy 2013. Springer.
Toxicities
• Chest: Chest wall toxicities, radiation pneumonitis, skin toxicities, brachial plexopathy, esophageal toxicities, and airway collapse
• Abdomen: Gastric/ duodenal ulcer, and RILD• Spine: Radiation myelopathy, vertebral
compression fracture, and pain flare
University Cancer Center
Toxicities
University Cancer Center
77 year old female with T1 N0 M0 non-small cell lung cancer was treated with 54 Gy in 3 fractions using SBRT (Left upper). She had no symptoms, but repeat imaging 6 months post treatment showed wedge like collapse of the segment just distal to her lesion (Right upper). A PET scan showed no uptake. A bronchoscopy showed airway irritation and mucous plugging, but brushings and washings showed no tumor cells (Right).
Courtesy of Professor Robert Timmerman
Toxicities
University Cancer Center
SBRT in 3 fractions to a total dose of 60 Gy
Courtesy of Professor Robert Timmerman
Toxicities
University Cancer Center
Courtesy of Professor Robert Timmerman
SBRT for stage I NSCLC in phase I trial; skin dose 24 Gy in 3 fxs; wet desquamation 6 weeks after SBRT (above and right); reaction resolved 3 months after SBRT (upper right)
Toxicities
University Cancer Center
Sahgal et al. IJROBP 2012
Toxicities
University Cancer Center
Sahgal et al. IJROBP 2012
gLQ model
gLQ model
gLQ model
Huang et al. Future Oncology 2013
Conclusions
• SBRT is one of the standard options for medically inoperable stage I NSCLC and oligometastases in the lung, liver and spine
• Other emerging applications include prostate cancer, renal cell cancer, pancreatic cancer, HCC, and recurrent head and neck cancer
• Multiple devices can be used to deliver SBRT
Conclusions
• Compared to CyberKnife, LINAC-based SBRT requires more manual work
• There are pros and cons to CyberKnife-based and LINAC-based SBRT
• Provided that all the basic principles are followed, it is possible to deliver high quality SBRT treatments with a LINAC with image-guidance features
Conclusions
• The experience of the team is likely more important than the actual device used
• When switching from CyberKnife-based to LINAC-based SBRT, it is crucial not to be too off-guard!
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